There are various methods available to isolate or separate biological molecules such as cells, antibodies, antigens, proteins, carbohydrates, nucleic acids, and the like. Magnetic separation techniques typically involve the application of a magnetic field to separate ferromagnetic particles contained within a fluid medium. Such techniques use devices that can be divided into two general types: an internal apparatus, or an external apparatus. In the internal apparatus, the ferromagnetic collection structure is contained within the fluid medium in order to intensify the applied magnetic field and improve the resultant gradient. One example of an internal apparatus involves packing steel wool or wires ("collection structures") into a column, wherein the column is situated adjacent to a magnet. A magnetic field is applied to the steel wires such that magnetic particles introduced into the column are attracted toward, and bind to, the steel wires. Another example of an internal apparatus involves loops of ferromagnetic wire that are inserted into a fluid medium. Drawbacks of such systems include entrapment of non-magnetic components; the potential for magnetic shielding of the collection structure therein; breakage of the collection structure during use and/or cleaning, and the requirement for cleaning or disposal of the collection structure between samples. In the external apparatus, generally the magnetic means is situated entirely externally with respect to the separation chamber. Typically, an external apparatus involves a plurality of magnets, or complex magnetic circuitry, placed around the periphery of the separation chamber; wherein the plurality of magnets, or the magnetic circuitry, produces a magnetic field gradient used to effect the magnetic separation. Drawbacks of the external systems include the need for intervention by the user to redesign the placement, positioning, or sizing of the plurality of magnets or circuitry to apply a magnetic field gradient to separation chambers of different sizes; and the additional need for manipulating multiple structures required for placement and positioning of the plurality of magnets or magnetic circuitry.
It is desirable, therefore, to provide a device for magnetic separation of components in a fluid that minimizes the amount of intervention necessary from a user. Additionally, it is desirable to provide a device for magnetic separation of components in a fluid that obviates the need for multiple structures for operation of the magnetic separation, and the manipulation associated with such structures.